A disc brake assembly typically includes a rotor and a caliper. The rotor is connectable to a hub of a rotatable axle. The caliper includes a mutually opposed pair of brake pads supported by a bracket. Each of the brake pads overlies a respective rotor braking surface. Normally, the caliper keeps the brake pads separated from the braking surfaces of the rotor. The braking system is activated by moving the pads into contact with the braking surfaces of the rotor; frictional interaction between the braking surfaces and the pads reduces or prevents rotation of the rotor relative to the caliper.
Brake squeal may be the result of modal excitations of the disc brake rotor (composed usually of cast iron) and the disc brake caliper by the frictional interaction of the brake pads. Countermeasures to reduce low-frequency brake squeal include increasing the stiffness of the caliper bracket by increasing the cross-sectional area of the tie-bars, and casting in or mechanically attaching a mass to the caliper bracket, wherein the mass acts as a vibration damper and/or changes the dynamic response of the caliper bracket.